Miller Electric S-21E User manual

MiIIe~
November1996 Form: TM-1571
Effective With Serial No. JJ507797
TECHNICAL MANUAL
Service And Parts
Wire Feed Equipment
A WARNING
SERVICING can be hazardous.
• Have all service procedures performed only by
qualified persons following standard safety
practices.
Use MILLER Testing Booklet (Part No.
150 853) when servicing this unit.
Use only genuine MILLER replacement
parts.
S-21E
U For help, call Factory ~U~r FAX: U Or write to:
Service Department: 14-735-4136 MILLER Electric Mfg. Co.
414-735-4505 L................J RO. Box 1079
Appleton, WI 54912 USA
coverjml — SB-124 467
© 1996 MILLER Electric Mfg. Co.
PRINTED IN USA

OM-1571B — 3/91
TABLE OF CONTENTS
Section No. Page No.
SECTION 1 - SAFETY PRECAUTIONS AND SIGNAL WORDS
1-1. General Information And Safety 1
1-2. Safety Alert Symbol And Signal Words 1
1-3. Safety Precautions 1
SECTION 2- SHIPPING AND STORAGE
2-1. Preparation For Reshipment 2
2-2. Storage 2
SECTION 3— SPECIFICATIONS
3-1. Description 3
SECTION 4- INSTALLATION OR RELOCATION
4-1. Location 3
4-2. Drive Roll Installation 3
4-3. Welding Gun Connections 5
4-4. Shielding Gas Installation 5
4-5. 14-Pin Plug Connection 6
4-6. Welding Wire Installation 6
4-7. Welding Wire Threading 7
4-8. Adjust The Hub Tension 8
4-9. Welding Cable Connection 8
4-10. Feeding Welding Wire 8
SECTION 5-OPERATOR CONTROLS
5-1. Power Switch 9
5-2. Wire Speed Control 9
SECTION 6— SEQUENCE OF OPERATION
6-1. Gas Metal Arc (GMAW) And Flux Cored Arc (FCAW) Welding 9
6-2. Shutting Down 10
SECTION 7- THEORY OF OPERATION
7-1. Theory Of Operation 10
Diagram 7-1. Block Diagram For Wire Feeder 11
Diagram 7-2. Block Diagram For SpotlBurnback Time Control Option 12

Section No. Page No.
SECTION 8- TROUBLESHOOTING
8-1. Testing Instruments And Information
8-2. Circuit Board Handling Precautions
8-3. Troubleshooting
Diagram 8-1. Troubleshooting Circuit Diagram For Wire Feeder
8-4. Motor Board PCi Testing Information
Diagram 8-2. Troubleshooting Circuit Diagram For Motor Control
Board PCi
8-5. Optional SpotlBurnback Board PC2 Testing Information
Diagram 8-3. Troubleshooting Circuit Diagram For Optional Spot/Burnback
Board PC2
SECTION 9- COMPONENT IDENTIFICATION AND LOCATION
Figure 9-1. Component Identification And Location
SECTION 10— MAINTENANCE
10-1. Routine Maintenance
10-2. Aligning Drive Roll And Wire Guide
10-3. Reinstallation Of Hub Assembly
10-4. Brush Inspection And Replacement
10-5. Overload Protection
SECTION 11 - ELECTRICAL DIAGRAMS
Diagram 11-1.
Diagram 11-2.
Diagram 11-3.
Diagram 11-4.
Diagram 11-5.
Circuit Diagram For S-21 E Effective With Serial No.
JJ507797 And Following
Wiring Diagram For S-21 E Effective With Serial No.
JJ507797 And Following
Circuit Diagram For Motor Control Board PCi Effective
With Serial No. JJ507797 And Following
Circuit Diagram For Optional SpotlBurnback Board PC2
Effective With Serial No. JJ507797 Thru JK742028
Circuit Diagram For Optional Spot/Burnback Board PC2
Effective With Serial No. JK742029 And Following
29
29
30
31
32
SECTION 12— PARTS LIST
LIST OF CHARTS AND TABLES
Table 3-1. Specifications
Table 8-1. Troubleshooting
Table 10-1. Maintenance Schedule
Table 11-1. List Of Circuit Diagrams And Wiring Diagrams
3
15
25
28
14
14
14
16
17
18
20
22
24
25
26
26
27
27

SECTION 1 - SAFETY PRECAUTIONS AND SIGNAL WORDS
1-1. GENERAL INFORMATION AND SAFETY
This manual provides theory of operation along with
specific operating, testing, and troubleshooting proce-
dures. It also includes precautionary information rele-
vant to these procedures. This manual can be an effec -
tive tool in the hands of a trained serviceperson. How-
ever, it does not and cannot take the place of previous
training nor safety-conscious service work. If any doubt
arises about the specific application of procedures pre -
sented, or if problems arise which are not covered in this
manual, contact the factory Service Department before
proceeding further.
1-2. SAFETY ALERT SYMBOL AND SIGNAL
WORDS
The following safety alert symbol and signal words are
used throughout this manual to call attention to and
identify different levels of hazard and special instruc -
tions.
This safety alert symbol is used with the signal
A
words WARNING and CAUTION to call atten -
tio n to the safety statements.
A
WARNING statements identify procedures or
practices which must be followed to avoid seri -
ous personal injury or loss of life.
CAUTION statements identify procedures or
A
practices which must be followed to avoid minor
personal injury or damage to this equipment.
IMPORTANT statements identify special instructions
necessary for the most efficient operation of this equip -
ment.
1-3. SAFETY PRECAUTIONS
A
W ARNING: ELECTRIC SHOCK can kill.
S Do not touch live electrical parts.
• Protect yourself with dry insulating gloves
and clothing.
• Insulate yourself from ground by using
rubber9loves and insulating floormats when
power is applied to the unit.
• Shut down unit and disconnect input power
when servicing unless the procedure specifi -
cally requires an energized unit.
• Do not leave live unit unattended.
ARC RAYS, SPARKS, AND HOT SURFACES
can burn eyes and skin; NOISE can damage
hearing.
• Wear correct eye, ear, and body protection.
FUMES AND GASES can seriously harm
your health.
• Keep your head out of the fumes.
• Ventilate to keep from breathing fumes and
gases.
• If ventilation is inadequate, use approved
breathing device.
• Read Material Safety Data Sheets (MSDSs)
and manufacturer’s instructions for any
materials used.
WELDING WIRE can cause puncture
wounds.
• Do not point gun towa rd any part of the body,
any conductive surface, or other personnel.
HOT METAL, SPATrER, AND SLAG can
cause fire and burns.
• Watch for fire.
• Have a fire extinguisher nearby and know
how to use it.
• Do not use near flammable material.
• Allow work and equipment to cool before
handling.
MOVING PARTS can cause serious injury.
• Keep away from moving parts.
HOT SURFACES can cause severe burns.
• Allow cooling period before servicing.
MAGNETIC FIELDS FROM HIGH CURRENTS
can affect pacemaker operation.
• Wearers should consult their doctor before
going near the servicing of arc welding equip -
ment or any arc welding operations.
5-21E TM-1571 Page 1

SECTION 2- SHIPPING AND STORAGE
A
PREPARATION FOR RESHIPMENT
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power employ -
ing lockout/tagging procedures before
preparing unit for shipping.
Lockout/tagging procedures forwire feedercon -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov-
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
1. Disconnect interconnecting cord from rear of wire
feeder.
2. Disconnect weld cable from drive assembly.
3. Disconnect and remove any remote controls or
devices.
4. Disconnect shielding gas (and water if applica -
ble) hoses from wire feeder.
5. Disconnect gun from wire feeder.
6. Secure welding wire to spool/reel, and remove
wire spool or reel from wire feeder.
7. Tape plastic around top and sides of unit.
8. Securely tie and/or tape cardboard over top and
around sides of unit. Use original shipping carton
if available.
IMPORTANT: Do not ship without a cardboard carton.
Not only do costs increase dramatically but the unit is
more subject to loss or damage without a carton.
9. If sending unit to factory, ship unit as directed by
factory Service Department or Transportation
Department.
A
STORAGE
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect in put power employ -
ing lockout/tagging procedures before storing
unit.
Lockout/tagging procedures forwirefeedercon -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov-
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
1. Disconnect interconnecting cord from rear of wire
feeder.
2. Disconnect weld cable from drive assembly.
3. Disconnect and remove any remote controls or
devices.
4. Disconnect shielding gas (and water if applica-
ble) hoses from wire feeder.
5. Disconnect gun from wire feeder.
6. Secure welding wire to spool/reel, and remove
wire spool or reel from wire feeder.
7. Clean outside of unit.
8. Remove wrapper.
9. Using dry compressed air, clean inside of unit.
10. Reinstall wrapper.
11. Select a storage location that least subjects the
unit to wide temperature variation, dust, dirt, and
corrosive vapors.
12. Carry unit to storage location.
13. Cover unit with plastic or suitable tarp.
TM-1571 Page 2 5-21E

SECTION 3- SPECIFICATIONS
Table 3-1. Specifications
Input Power
Requirements Electrode
Wire
Diameter Capacity Wire
Spool
Capacity
Electrode Wire
Feed Speed
Weight
Net Ship
10 to 20 lb.
24 VAC
3.5 Amps
50/60 Hz
.O23thru .045 in.
(0.6 thru 1.1 mm)
(4.5 to 9 kg)
8 in. (203mm) spools
up to 60 lb.
(27.2 kg)_coils
75-600 ipm
(1.9-15.2 mom)
at 24 VA~
30 lbs.
(13.6 kg)
33 lbs.
(15 kg)
SB-124 467
Figure 3-1. Overall Dimensions
3-1. DESCRIPTION
This unit is a semiautomatic constant speed wire feeder
which operates on 24 volts ac. The feeder is designed
for connection to a constant voltage (CV) type power
source through a 14-pin connector. If 115 volts ac is the
only power available for use with the feeder, the optional
power supply adapter Model PSA-2 115/24 should be
used to convert the power to 24 volts ac.
The case can be tightly latched to help keep out dust and
dirt.
SECTION 4- INSTALLATION OR RELOCATION
4-1. LOCATION (Figure 3-1)
The service life and efficiency of this unit and associated
components are reduced when they are subjected to
high levels of dust, dirt, moisture, corrosive vapors, and
extreme heat.
A proper installation site should be selected for the wire
feeder if the unit is to provide dependable service. Lead
lengths must be considered when installing the unit. A
slot is provided in the base of the unit to fit over the lifting
eye on welding power sources so equipped. Suitable
space should be maintained around the unit for making
necessary connections and for maintenance functions.
4-2. DRIVE ROLL INSTALLATION (Figure 4-1)
A
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power employ -
ing lockout/tagging procedures before in -
specting or installing.
Lockout/tagging procedures for wire feeder con -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov-
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators. TM-1571 Page 3
10-112 In.
(267 mm)
22-1(2 in.
(572 mm)
S-21E

• OPTIONAL
Pressure Roll
Assembly
(Shown In Open
PosItion)
It is necessary to install the required drive rolls when set -
ting up this unit and also when changing wire sizes.
IMPORTANT: Base drive roll selection on the following
recommendations:
The dual-grooved drive roll provided with the feeder ac -
commodates .023 through .045 in. (0.6 through 1.1 mm)
wire. This drive roll has both a “‘I” groove and a “‘I”
knurled groove. Use the “V” groove for feeding .023 and
.030 in. (0.6 and 0.76 mm) wire. Use the “V” knurled
groove for feeding .035 and .045 in. (0.89 and 1.1 mm)
wire. The wire size for each groove is stamped on the
side of the drive roll. When the drive roll is installed in the
feeder, the wire size stamp for the unused groove will be
visible.
The 50 Series wire feeder style drive rolls may be used
with this feeder, but, due to the flat idler pressure roll
used, a knurled drive roll is recommended when feeding
.035 and .045 (.089 and 1.1 mm) wire.
A
W ARNING: ELECTRIC SHOCK can kill.
Do not store metallic objects in this compart -
ment. The motor drive assembly is electri -
cally hot whenever the welding circuit is ener -
gized.
Loose metal objects in this compartment may
create an electrical path between the weld out -
put circuit and any metal surfaces or compo-
nents resulting in electric shock.
IMPORTANT: Both types of 50 Series style drive rolls
can be reversed for reuse when they become worn. Re -
verse rolls to position unused groove(s) to feed wire.
The dual-grooved drive roll pro vided with this feedercan
be reversed, but only to feed a different size wire.
1. Unlatch and open left case access door.
2. Loosen pressure adjustment knob, and pivot
knob free of pressure arm.
3. Pivot pressure arm away to expose drive roll
carrier.
4. For dual-grooved roll supplied with feeder:
a. Choose the proper groove.
b. Slide drive roll onto drive roll mounting hub with
chosen groove toward inside of machine. The
wire size for the unused groove will be visible
after installation.
c. Align the drive roll with holes.
d. Insert securing screws, and tighten.
Hub
Wire
• Spring
9
Retaining
Ring
Ret. 50497
Figure 4-1. Wire Feeder Components
GunlFeeder
connector
Securing Knob
Ref. SB-125 923
TM-1571 Page 4
5-21E

5. For 50 Series style one-piece drive rolls: B. Gun Trigger (Figure 5-1)
a. Slide drive roll onto drive roll mounting hub.
b. Align drive roll with holes.
c. Insert securing screws, and tighten.
6. For 50 Series style split drive rolls:
a. Align holes on pair of split drive rolls.
b. Insert securing screw.
c. Slide drive rolls onto drive roll mounting hub.
d. Align drive rolls with holes.
e. Insert securing screws, and tighten.
IMPORTANT: Horizontal alignment of the drive roll on
the drive roll mounting hub with the wire guide is factory
set and should not require readjustment. If readjustment
becomes necessary, see Section 10-2.
7. Close and secure left case access door.
4-3. WELDING GUN CONNECTIONS (Figures 4-1
And 5-1)
A
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power employ -
ing lockout/tagging procedures before work -
ing on feeder.
Lockout/tagging procedures for wire feeder con -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov-
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
IMPORTANT: A hole ispro vided in the nameplate form-
stallation of a gun requiring an opening for an external
gas line. Remove snap-in blank before installation.
A. Gun Connector To Drive Assembly (Figure 4-1)
1. Unlatch and open left case access door.
2. Loosen gun/feeder connector securing knob on
the wire drive housing.
3. Insert gun/feeder connector through the access
hole in the front panel.
4. Insert gun/feeder connector into drive housing
with the outlet wire guide as close to the drive rolls
as possible without touching, and tighten the se -
curing knob.
5.
S-21E
Close and secure left case access door.
‘9=
TRIGGER
RECEPTACLE
Connect gun trigger plug to trigger receptacle on the
front panel as follows: align keyways, insert gun plug
into trigger receptacle, and rotate threaded collar fully
clockwise.
4-4. SHIELDING GAS INSTALLATION (Figures
4-2 And 4-3)
A
WARNING: PRESSURIZED CYLINDERS can
rupture causing serious personal injury and
loss of life; FALLING CYLINDERS can cause
serious injury and equipment damage.
• Keep cylinders away from welding or other
electrical circuits.
• Never allow a welding electrode to touch any
cylinder.
• Always fasten cylinder securely to running
gear bracket, a wall, or other stationary sup-
port.
A. Gas Cylinder (Customer Supplied)
Chain the cylinder to a wall or other stationary support to
prevent the cylinder from falling over and breaking off
the valve. If optional power source running gear is used,
secure gas cylinder to running gear with supplied chain.
B. Regulator/Flowmeter (Customer Supplied)
1. With the cylinder securely installed, remove the
cylinder cap, stand to one side of cylinder valve,
and open valve slightly. When gas flows from cyl -
inder, close valve. This procedure blows out dust
or dirt that may have accumulated around the
valve seat.
IMPORTANT: A gasket should be installed to prevent
leaks. Do not use lubricants or sealing agents.
2. The regulator/flowmeter must be properly
equipped with a stem, nut connectors, and gas -
ket for use with either CO2
cylinders or inert gas
type cylinders.
3. Install gas regulator/flowmeter onto gas cylinder
valve; keep the face of the regulator/flowmeter
gauge in vertical position, and tighten stem nut
securely to gas cylinder valve.
4. A shielding gas fitting is provided on the rear of
the wire feeder. Obtain a suitable hose with
5/8-18 right- hand fitting. Attach one end of the
gas hose to this fitting. Attach the other end of the
gas hose to the regulator/flowmeter.
TM-1571 Page 5

Figure 4-2. Typical RegulatorlFlowmeter Installation
4-5. 14-PIN PLUG CONNECTION (Figures 4-3 And
4-4)
The 14-pin plug PLG1 00, on the end of the interconnect -
ing cord, provides a junction point for connecting the
wire feeder to a welding power source. This connection
provides 24 volt ac power, and contactor control when
used with a constant voltage (CV) power source with a
14-pin receptacle. To make connections, align keyway,
insert plug, and rotate threaded collar fully clockwise.
The pins on plug PLG 100 are defined in relation to both
the power source and wire feeder. The welding power
source provides six functions to the wire feeder. The
pins are designated as follows:
Pin A: Up to 10 amperes of 24 volts ac, 60 Hz, with re -
spect to socket G (circuit common); protected by fuse in
welding power source.
Pin B: 24 volts ac input power to energize the weld con -
tactor. The feeder sends back 24 volts ac by means of a
contact closure from pin A to pin B.
Pin G: 24 volts ac circuit common; also connected to
welding power source chassis.
IMPORTANT: The remaining pins in the receptacle are
not used by the feeder.
Shielding Gas
valve Fitting,
14-Pin
Plug
Gas cylinder
Valve
Argon or Argon
Mix cylinder
SB-109 492
Ref. S-0004
Figure 4-4. Front View Of 14-Pin Plug With Pin
Locations
4-6. WELDING WIRE INSTALLATION (Figure 4-5)
A
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power em ploy -
ing lockout/tagging procedures before work -
ing on feeder.
Lockout/tagging procedures forwire feeder con -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov-
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
A
CAUTION: LOOSE WELDING WIRE can
cause Injury.
• Keep a firm hold on the wire during installa -
tion, removal, and threading operations.
Spooled wire has a tendency to unravel rapidly
when loosened from the spool.
SA-125 924 IMPORTANT: If it should become necessary to replace
any part of the hub assembly see hub assembly rein -
stallation instruction in Section 10-3.
Flow
Adjustment
CO2
Washer CO2 cylinder
CO2 Installation Argon Installation
Wire Feed
Weld Cable
Connection
Opening
Figure 4-3. Rear Panel View
TM-1571 Page 6 5-21E

A. Installation Of Spool-Type Wire (Figure 4-1) 4-7.
WELDING WIRE THREADING
1. Remove retaining ring from hub.
2. Slide wire spool on hub so that wire feeds off the
bottom of the spool.
3. Rotate wire spool until hole in spool slides over
pin in hub and seats against back flange of the
hub.
4. Insert optional compression spring if required.
5. Reinstall retaining ring to secure wire spool on
hub.
B. Installation Of Optional Wire Reel And Reel-
Type Wire (Figure 4-5)
1. Remove retaining ring and, if applicable, wire reel
assembly from hub.
2. Lay wire reel assembly flat on a table or floor.
3. Remove spanner nut from wire reel assembly.
4. Remove wire retainer, and install wire onto wire
reel. Be sure that wire feeds off bottom of reel.
5. Reinstall wire retainer and spanner nut onto wire
reel.
6. Slide wire reel assembly onto hub, and rotate as -
sembly until hub guide pin is seated in reel.
7. Reinstall retaining ring onto hub.
• Spanner
Nut
• OPTIONAL
Figure 4-5. Optional Wire Reel And Reel-Type Wire
Installation
A
A
WARNING: ELECTRIC SHOCK can kill;
MOVING PARTS can cause injury.
• Do not touch live electrical parts.
• Keep clear of pinch points.
• Do not energize welding power source or wirE
feeder until instructed to do so.
The welding wire and all metal parts in contaci
with it are energized while welding.
WELDING WIRE can cause puncture
Wounds; HOT SURFACES can burn skin.
• Do not depress gun trigger untll instructed tc
do so.
• Do not point gun towa rd any part of the body
any conductive surface, or other personne.
when threading welding wire.
• Allow gun to cool before touching.
FLYING DIRT AND METAL PARTICLES can
injure personnel and damage equipment.
• Point gun liner only in a safe direction awaj~
from personnel and equipment when clean~
ing with compressed air.
Blow out the gun wire
9uide liner with com -
pressed air when changing wire. This will re -
move any metal chips and dirt that may have ac -
cumulated.
CAUTION: LOOSE WELDING WIRE can
cause Injury.
• Keep a firm hold on the wire during installa -
tion, removal, and threading operations.
Spooled wire has a tendency to unravel rapidly
when loosened from the spool.
1.Install the wire as instructed in Section 4-6.
2. Cut off any portion of the free end of the wire
which is not straight. Be sure that the cut end is
free from rough surfaces to permit proper feed -
ing.
3. Adjust hub tension according to Section 4-8 if
necessary.
4. Loosen the pressure adjustment knob on the wire
drive housing, and pivot the pressure arm open.
5. Feed the wire through the inlet wire guide, past
the drive rolls, and on into the gun. Feed approxi -
mately 4 inches (102 mm) of wire into the gun.
6. Close the pressure lever, and secure with pres -
sure adjustment knob making sure the welding
wire is in the drive roll groove and properly
aligned with the inlet and outlet guides (outlet
guide is part of gun).
7. Tighten the pressure adjustment knob to obtain
the proper clamping pressure on the welding
wire. Do not overtighten. Further adjustment can
•Wlre Retainer
SC-127 306
S-21E TM-1571 Page 7

be made when the wire feeder is put into
operation.
4-8. ADJUST THE HUB TENSION (Figure 4-1)
A
CAUTION: LOOSE WELDING WIRE can
:ause Injury.
Keep a firm hold on the wire during installa -
tion, removal, and threading operations.
Spooled wire has a tendency to unravel rapidly
when loosened from the spool.
Check the hub tension by slowly pulling the wire toward
the drive roll. The wire should unwind freely, but have
sufficient tension to keep the wire taut and prevent back -
lash when wire feeding stops. If adjustment is neces -
sary, loosen or tighten the hex nut on the end of the hub
support shaft accordingly.
4-9. WELDING CABLE CONNECTION
A
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power employ -
ing lockout/tagging procedures before mak -
ing weld cable connections.
Lockout/tagging procedures forwire feedercon -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov -
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
1. Unlatch and open left case access door.
2. Route weld cable through weld cable connection
opening on rear of unit (see Figures 4-1 and 4-3).
3. Connect end of cable to terminal on bottom of
drive assembly. Be sure that terminal is clean
and bolt is secure.
4. Close and secure left case access door.
4-10. FEEDING WELDING WIRE
A
WARNING: ELECTRIC SHOCK can kill;
MOVING PARTS can cause Injury.
• Do not touch live electrical parts.
• Keep away from pinch points.
• Do not energize welding powersource or wirE
feeder until instructed to do so.
The welding wire and all metal parts in contaci
with it are energized while welding.
WELDING WIRE can cause puncture Wounds;
HOT SURFACES can burn skin.
• Do not depress gun trigger until instructed to do
so.
• Do not point gun toward any part of the body
any conductive surface, or other personnel
when threading welding wire.
• Allow gun to cool before touching.
1. Be sure wire is installed as instructed in Section
4-7.
2. Be sure gun is installed according to Section 4-3
of this manual and the gun Owner’s Manual.
3. Cut off any portion of the free end of the wire
which is not straight. If necessary, straighten wire
to remove cast. Be sure that the cut end is free
from rough surfaces to permit proper feeding.
4. Lay gun cable assembly out flat and straight (no
coils in the cable/conduit).
5. Energize the welding power source.
6. Place the wire feeder POWER switch in the ON
position.
A
WARNING: ELECTRIC SHOCK can kill; TAN -
GLED WELDING WIRE can touch case caus-
ing Welding power source open-circuit volt -
age to be present on case if gun trigger is
pressed.
• Do not touch wire feeder case if gun trigger is
pressed, and wire does not feed.
• If wire stops feeding, tum off welding power
source, and determine the cause.
• Correctanyhub tension, jammed wire, or gun
liner damage problems before trying to con-
tinue welding.
7. Press the gun trigger (see WARNING block at be -
ginning of the Section). Wire feeds if drive roll
pressure is properly adjusted to prevent slippage.
If wire slippage is noticed, adjust hub tension ac -
cording to Section 4-8. If excessive pressure is
required, check gun contact tube and gun liner for
correct size or obstructions. Release the trigger
when welding wire extends approximately one
inch (25 mm) out of gun tip.
8. Shut down wire feeder and welding power
source.
TM-1571 Page 8
S-21E

SECTION 5- OPERATOR CONTROLS
5-1. POWER SWITCH (Figure 5-1)
POWER
The POWER switch functions as the ON/OFF switch for
the wire feeder.
5-2. WIRE SPEED CONTROL (Figure 5-1)
WIRE SPEED
ojo
The WIRE SPEED control adjusts the wire feed speed
88-124 467 in inches per minute within the wire speed range. Rotat -
ing the WIRE SPEED control clockwise increases wire
feed speed. The scale is calibrated in inches per minute.
SECTION 6— SEQUENCE OF OPERATION
6-1. GAS METAL ARC (GMAW) AND FLUX
CORED ARC (FCAW) WELDING
A
WARNING: ELECTRIC SHOCK can kill;
MOVING PARTS can cause serious injury;
EXPOSURE TO ENVIRONMENT can damage
internal parts.
• Do not touch live electrical parts.
• Keep case closed while operating.
Warranty is void if the wire feeder is operated
with any portion of the outer enclosure open or
removed.
ARC RAYS can burn eyes and skin; NOISE
can damage hearing.
• Wear correct eye, ear, and body protection.
FUMES AND GASES can seriously harm
your health.
• Ventilate to keep from breathing fumes and
gases.
• If ventilation is inadequate, use approved
breathing device.
HOT METAL, SPATrER, AND SLAG can
cause fire and burns.
• Watch for fire.
• Keep a fire extinguisher nearby and know
how to use it.
• Allow work and equipment to cool before
handling.
MAGNETIC FIELDS FROM HIGH CURRENTS
can affect pacemaker operation.
• Wearers should consult their doctor before
going near arc welding gouging, or spot
5-21 E welding operations.
WELDING WIRE can cause puncture
Wounds.
• Do not point gun toward any part of the body
any conductive surface, or other personnel.
1. Install and connect unit according to Section 4.
2. Wear dry insulating gloves and clothing.
3. Connect work clamp to clean, bare metal at work-
piece.
4. Rotate WIRE SPEED control to desired position
(see Section 5-2).
A
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Do not touch welding wire or any metal part in
contact with it while welding.
The welding wire and all metal parts in contact
with it carry weld output when the welding power
source contactor is energized.
5. Energize the welding power source or generator.
6. Place the POWER switch in the ON position
7. Turn on shielding gas at the source, if applicable.
8. Wear welding helmet with proper filter lens
according to ANSI Z49.1.
9. Hold tip of gun approximately 1/2 in. (13 mm)
from workpiece, and depress gun trigger. Current
flows, gas flows, and wire feeds. If wire slippage
is noticed, adjust drive roll pressure according to
Section 4-7.
Access Hole For
Gun/Feeder Connector
Gun Trigger
Receptacle
Wire Speed
Control
Figure 5-1. Control Panel View
TM-1571 Page 9

WARNING: ELECTRIC SHOCK can kill;
TANGLED WELDING WIRE can touch case
causing welding power source open-circuit
voltage to be present on case if gun trigger is
pressed.
• Do not touch wire feeder case if gun trigger is
pressed and wire does not feed.
• If wire stops feeding, turn off welding power
source, and determine the cause.
• Correctanyhub tension,jammed wire, or gun
liner damage problems before trying to
continue welding.
6-2. SHUTTING DOWN
1. Stop welding.
2. Place POWER switch in the OFF position.
3. Shut down welding power source or generator.
4. Turn off shielding gas at source, if applicable.
A
WARNING: HIGH CONCENTRATION OF
SHIELDING GAS can harm health or kill.
• Shut off gas supply when not in use.
SECTION 7- THEORY OF OPERATION
7-1. THEORY OF OPERATION
IMPORTANT: The following Theory Of Operation is
written in steps which match the circled numbers on Dia-
grams 7-1 and 7-2.
Wire Feeder Without Options (Diagram 7-1)
The 14-pin plug PLG100 on the end of the inter -
connecting cord provides 24 volts ac input power
from the welding power source and provides con-
tactor control to the welding power source.
2. POWER switch 51 provides on/oft control of 24
volts ac input power to the wire feeder.
3. Circuit breaker CB1 provides overload protection
for the wire feeder.
4. Motor Board PCi regulates the speed of wire
drive motor Ml as set by WIRE SPEED control
R32. PCi also controls gas valve 051 and weld-
ing power source contactor via control relay
CR1.
5. Gas valve 051 provides shielding gas during the
weld cycle.
6. Integrated rectifier SRi converts the 24 volts ac
input power to a rectified 35 volts dc.
Capacitor Cl provides filtering for the 35 volts dc.
Voltage regulator VR1 reduces the 35 volts dc in -
put voltage to 24 volts dc for control circuitry on
PCi and trigger receptacle RC1 01.
9. Trigger receptacle RC1 01 provides the trigger in -
put signal to the motor stop/start circuitry.
A.
1.
7.
8.
10. Motor stop/start circuitry provides input to the
brake turn on ramp, phase modulation, and con-
trol relay circuitries.
11. Control relay CR1 controls gas valve 051 and the
welding power source contactor through 14-pin
plug PLG100.
12. Brake circuitry transistor Q7 provides an electri -
cal path for motor current during braking.
13. Turn on ramp provides power to WIRE SPEED
control R32.
14. WIRE SPEED control R32 provides a signal to
the comparator circuitry to control the wire speed.
15. Feedback circuitry provides comparator circuitry
with a feedback signal of actual motor voltage.
16. Comparator circuitry compares feedback signal
to R32 control signal and adjusts phase modula -
tion circuitry accordingly.
17. Phase reset transistors Q5 and Q6 reset the tim -
ing of phase modulation.
18. Unijuction transistor Qi creates the phase modu -
lation from the charging of capacitor ClO.
19. Pulse transformer Ti transfers the phase modu -
lated signal to the gates of SCRi and SCR2.
20. Drive SCR’s SCRi and SCR2 turn on from the
phase modulation signal and supply power to
wire drive motor Mi.
21. Wire drive motor Ml feeds the welding wire.
A
TM-1571 Page 10
S-21E

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S-21E TM-1571 Page 11

B. SpotlBurnback Time Control Option (Diagram
7-2)
1. Optional Spot/Burnback Board PC2 provides
control of spot weld time and adjustment of burn-
back time.
2. Burnback potentiometer R26 allows adjustment
of the burnback time between 0.02 and 0.25 sec-
onds.
3. Spot time potentiometer R25 allows adjustment
of spot time from 0.12 to 2.5 seconds or 0.25 to 5
seconds depending on the setting of Spot Time
DIP Switch Sl.
4. Spot/Continuous switch S51 allows either a nor -
mal untimed weld cycle or a timed spot weld
cycle.
5. Spot time DIP switch 51 provides a selection of
short range (0.12 to 2.5 seconds) or long range
(0.25 to 5 seconds) spot time.
Diagram 7-2. Block Diagram For Spot/Burnback Time Control Option
TM-1571 Page 12 S-21E

S-21E TM-1571 Page 13
Notes

SECTION 8— TROUBLESHOOTING
A
8-1. TESTING INSTRUMENTS AND INFORMA -
TION
The service procedures in this manual require proper
testing instruments. Use a good quality digital volt-
ohmmeter (DVM) with one megohm input impedance or
greater and diode check capability (use an analog VOM
for variable resistor testing). If an oscilloscope is speci -
fied, use a good quality unit with one megohm input im -
pedance or greater. If a circuit board has a protective
coating, it will be necessary to remove coating or use
needle probes in the test area to obtain proper contact.
Recoat areas if necessary to retain corrosion protection.
Digital volt-ohmmeters (DVM’s) do not require lead po -
larity attention when making connections. However, the
meter may indicate a — (negative) voltage when the test
procedure specified a + (positive) voltage. If the incor -
rect polarity appears on the display, reverse meter lead
connections to test points.
8-2. CIRCUIT BOARD HANDLING PRECAUTIONS
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power employ -
ing lockout/tagging procedures before
inspecting, maintaining, or servicing.
Lockout/tagging procedures forwirefeedercon -
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov -
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
MOVING PARTS can cause serious injury.
• Keep away from moving parts.
HOT SURFACES can cause severe burns.
• Allow cooling period before servicing.
CAUTION: ELECTROSTATIC DISCHARGE
(ESD) can damage circuit boards.
• Put on properly grounded wrist strap
BEFORE handling circuit boards.
• Transport circuit boards in proper static-
shielding carriers or packages.
• Perform work only at a static-safe work area.
INCORRECT INSTALLATION or misaligned
plugs can damage circuit board.
• Be sure that plugs are properly installed and
aligned.
EXCESSIVE PRESSURE can break circuit
board.
• Use only minimal pressure and gentle move -
ment when disconnecting or connecting
board plugs and removing or installing board.
A
8-3. TROUBLESHOOTING (Table 8-1 And Dia -
gram 8-1)
A
WARNING: ELECTRIC SHOCK can kill.
• Do not touch live electrical parts.
• Shut down wire feeder and welding power
source, and disconnect input power employ -
ing lockout/tagging procedures before
inspecting, maintaining, or servicing.
Lockout/tagging procedures forwire feeder con-
sist of disconnecting interconnecting cord, and
for welding power source consist of padlocking
line disconnect switch in open position, remov -
ing fuses from fuse box, or shutting off and red-
tagging circuit breaker or other disconnecting
device. Stop engine, and disconnect negative
(—) battery cable from battery on welding gen -
erators.
MOVING PARTS can cause serious injury.
• Keep away from moving parts.
HOT SURFACES can cause severe burns.
• Allow cooling period before servicing.
Troubleshooting to be performed only by
qualified persons.
The troubleshooting table is designed to diagnose some
of the troubles that can develop in this wire feeder. Any
circuit normally tied to ground must be at ground poten -
tial.
Use the table in conjunction with the diagrams in this
manual and the exploded views and component values
in the Service Parts Manual while performing tro -
ubleshooting procedures.
When replacing components, use only genuine MILLER
replacement parts. MILLER parts are required for war-
ranty repair by authorized warranty service agency.
Resistance and continuity measurements must be
made with the unit shut down. Isolate components be-
fore making resistance and continuity measurements.
IMPORTANT: Before beginning troubleshooting proce -
dures, visually examine internalcomponents for signs of
overheating and failure. Many major problems, such as
winding(s) failure are usually apparent by discoloration,
smoke, and smell. Fortunately most elect rical pro blems
are relatively simple: blown fuses, tripped circuit break -
ers, incorrect switch positions, loose connections, cor -
rosion, and the like. A complete, careful inspection often
saves considerable time, money and frustration.
IMPORTANT: Be sure that all connections are correct
and secure according to Section 4 and that all controls
and switches are in proper positions before proceeding
with troubleshooting.
TM-1571 Page 14
S-21E

Table 8-1. Troubleshooting
TROUBLE CAUSE REMEDY
Wire does not feed. Circuit breaker CB1. Check gun liner, hub tension, and drive roll
pressure (see Section 4). Reset CBl (see Sec
tion 10-5).
Loose or improperly made gun
trigger connection. Check
gun trigger connection (see Section
4-3).
Gun trigger. See gun Owner’s Manual.
Welding gun shorted. Repair or replace welding gun.
Motor Ml. Check connections for continuity to Ml. Check
motor brushes (see Section 10-4). Replace Ml
if necessary.
Motor Control Board PCi or
poor connections to PCl.
Check connections for continuity to PCl.
Check PCi according to Diagram 8-2 and Sec
tion 8-4. Replace PCl if necessary.
Wire feeds erratically. Pressure on drive roll is insuf-
ficient.
Rotate pressure adjustment knob counter
clockwise in 1/4 turn increments until the wire
stops slipping (see Section 4-2).
Drive roll wrong size for wire
size used.
Change to correct size drive roll (see Section
4-2).
Drive rolls worn. Replace drive rolls (see Section 4-2).
Dirt in drive rolls. Clean drive rolls (see Section l0-lC).
Motor Control Board PCl or
poor connections to PCi.
Check connections for continuity to PCi.
Check PCi according to Diagram 8-2 and Sec
tion 8-4. Replace PCi if necessary.
Wire feeds but there is no gas
flow.
Gas valve GSl. Check GS1 for proper coil voltage and connec
tions (see Diagram 8-1). Check continuity of coil.
Replace GSl if necessary.
Motor Control Board PCl or
poor connections to PCl.
Check connections for continuity to PCl.
Check PCl according to Diagram 8-2 and Sec
tion 8-4. Replace PCl if necessary.
Wire does not feed until trigger
is pulled but continues to feed
after trigger is released.
Welding gun is shorted be-
tween one of the trigger leads
and weld cable.
Repair or replace welding gun.
Gun nozzle opening restricted. Weld spatter or foreign matter
accumulation.
Carefully remove any weld spatter or foreign
matter which may accumulate around the
nozzle opening. Use a hardwood stick, never a
metal tool.
The gas valve in the feeder is
rattling loudly along with possi-
ble erratic or slow wire feed
speed.
Welding gun is shorted be-
tween one of the trigger leads
and weld cable.
Repair or replace welding gun.
Motor runs but wire is not ener-
gized with Spot/Burnback Op-
tion installed.
Spot/Burnback Board PC2 or
poor connections to PC2.
Check connections for continuity to PC2. Check
PC2 according to Diagram 8-3 and Section 8-5.
Replace PC2 if necessary.
TM-i 571 Page 15
5-21E

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